Attention and tactile processing in the somatosensory system. Funds are requested to continue our studies on understanding how selective attention effects the responses of neurons in the somatosensory system. The broad aim of these studies is to determine the neural mechanisms underlying shape processing in the somatosensory system. In this proposal, we focus our efforts on determining how information about the orientation of edges contacting multiple locations on the two hands interact. The study builds on our previous findings showing that: 1) There is a robust representation in the second somatosensory (SII) cortex of the orientation of edges contacting multiple digits, and 2) Most of the neurons in SII are affected by the animal's focus of attention. The first aim is to determine how single and multiple edges presented within and across finger pads of the same and opposite hands are represented in the somatosensory system. In these studies, we record from neurons in areas 3b, 1, 2 and SII cortex in animals performing a visual discrimination task, while simultaneously stimulating different combinations of the proximal, middle and distal phalanges on digits 2-4 on both hands with single or multiple oriented edges. These experiments will determine how edge information is integrated across digits. The second aim is to determine how selective attention affects the representation of edge information when single and multiple edges are presented to the hands. During the experiment, the edges will be placed both inside and outside the neuron's receptive field while animals perform tactile discrimination tasks. In some experiments, animals will be trained to discriminate the orientation of single edges, and in others, animals will be trained to compare the orientations of two edges presented simultaneously to the hands. These experiments will determine how selective attention modifies the receptive field structures of neurons, and will determine whether neurons at higher levels in the somatosensory cortex are tuned to coherent edges that span multiple digits.